1. Field of the Invention
The present invention relates to a rolling bearing which comprises a pair of races, rolling elements and a cage and in which a region defined between both the races is filled with a solid lubricating composition which is composed of a mixture of a resin and a lubricating component, and a method of fabricating the same.
2. Description of Related Art
A lubricating component such as lubricating oil or grease is generally used for lubricating a rolling bearing. The lubricating component is scattered at the time of rotation of the rolling bearing because it has flowability. As a result, the lubricating component must be frequently supplied.
Furthermore, the lubricating component such as lubricating oil or grease is helpless against entrance of water, dust, dirt, and the like from outside the rolling bearing. In the case of a rolling bearing used in an environment which makes the entrance of water, dust, dirt, and the like easy, sealing members with a complicated structure must be provided.
In order to solve the above-mentioned problems, a lubricating composition formed by solidifying a mixture of a resin such as polyethylene and the above-mentioned lubricating component is provided (see, for example, unexamined, Japanese Patent Publication No. 54-22415 (1979), Japanese Patent Publication No. 63-23239 (1988), and Japanese Patent Publication No. 3-67559 (1991). The solid lubricating composition is obtained by filling a region inside a rolling bearing with the mixture in a fluid shape, then heating the mixture to not less than the melting point of the resin and then cooling the heated mixture.
The solid lubricating composition exhibits lubricating properties as a result of gradual seepage of the lubricating component caused by centrifugal force or heat at the time of use of the rolling bearing. Consequently, the lubricating component may not be scattered at the time of rotation of the rolling bearing, whereby the lubricating component need not be supplied over a long time period.
When the lubricating composition is solidified by fully filling the region inside the rolling bearing, it functions as a barrier against water, dust, dirt, and the like from outside the rolling bearing, whereby it is considered that sealing members can be abandoned.
In this case, however, friction arises between the solidified lubricating composition and each of members constituting the rolling bearing (that is, an inner race, an outer race, rolling elements and a cage), and the friction is increased at the time of rotation of the rolling bearing as the whole, whereby it is expected that torque generated by the rolling bearing is increased.
On the other hand, when a clearance between the cage and the rolling elements, for example, is partially filled with the lubricating composition in order to decrease the torque generated by the rolling bearing, the function of the lubricating composition as the barrier against water, dust, dirt, and the like from outside the rolling bearing is lost, whereby sealing members with a complicated structure must be absolutely provided.